ardor vs zeal

ardor

noun
  • Spirit; enthusiasm; passion. 

  • Intense heat. 

  • Great warmth of feeling; fervor; passion. 

zeal

noun
  • The fervour or tireless devotion for a person, cause, or ideal and determination in its furtherance; diligent enthusiasm; powerful interest. 

  • The collective noun for a group of zebras. 

How often have the words ardor and zeal occurred in a corpus of books? (source: Google Ngram Viewer )